What Is -- and What Isn't --
Evidence of Global Warming

All
the evidence we've heard regarding global warming never constituted, in
any manner, actual evidence that it was taking place.

"Climategate" has everybody rethinking global warming.
Many are
wondering -- if leading scientists were tempted to finagle their data,
is the evidence for catastrophic climate change weaker than previously
thought?

Actually, the evidence was never even evidence.

There is a fundamental misunderstanding -- shared by
nearly everybody
about the nature of anthropogenic global warming theory (AGW) -- over
exactly what constitutes evidence for that theory and what does not.

Remember when we heard that the icebergs were melting,
that polar
bears were decreasing in number, that some places were drier than usual
and that others were wetter, that the ocean was growing saltier here
and fresher there, and that hurricanes were becoming more terrifying?
Remember the hundreds of reports on what happens when it gets hot
outside?

All of those observations might
have been true, but absolutely none of them were
evidence of AGW.

Diminishing glaciers did not prove AGW; they were
instead a
verification that ice melts when it gets hot. Fewer polar bears did not
count in favor of AGW; it instead perhaps meant that maybe adult bears
prefer a chill to get in the mood. People sidling up to microphones and
trumpeting "It's bad out there, worse than we thought!" was not
evidence of AGW; it was evidence of how easily certain people could
work themselves into a lather.

No observation of what happened to any particular thing
when the air was warm was direct evidence of AGW. None of it.

Every breathless report you heard did nothing more than
state the
obvious: Some creatures and some geophysical processes act or behave
differently when it is hot than when it is cold. Only this, and nothing
more.

Can you recall where you were when you heard that global
warming was
going to cause an increase in kidney stones, more suicides in Italy,
larger grape harvests in France, and smaller grape harvests in France?
How about when you heard that people in one country would grow
apathetic, that those in another would grow belligerent, and -- my
favorite
-- that prostitutes would be on the rise in the Philippines? That the
world would come to a heated end, and that women and minorities would
be hardest hit?

Not a single one of these predictions was ever
evidence of AGW.

For years, it was as if there was a contest for the most
outlandish claim of what might happen if
AGW were true. But no statement of what might
happen if AGW is true is evidence for
AGW. Those prognostications were only evidence of the capacity for
fanciful speculation. Merely this and nothing more.

So if observations of what happens when it's hot outside
don't
verify AGW, and if predictions of what might happen given AGW were true
do not verify AGW, what does? Why did people get so excited?

In the late 1990s, some places on Earth were hotter than
they were
in the late 1980s. These observations were indirect -- and not direct --
evidence of AGW. The Earth's climate has never been static;
temperatures sometimes rise and sometimes fall. So just because we see
rising temperatures at one point does not prove AGW is true. After all,
temperatures have
been falling
over the last decade, and AGW supporters still say their theory is
true. Rising -- or falling -- temperatures are thus consistent with many
theories of climate, not just AGW.

Climate scientists then built AGW models, incorporating
the observed
temperatures. They worked hard at fitting those models so that the
models could reproduce the rising temperatures of the 1990s, while at
the same time fitting the falling temperatures of the 1970s, etc. They
had to twist and tweak -- and with the CRU
emails,
it now appears they twiddled. They had to cram those observations into
the models and, by God, make them fit, like a woman trying on her
favorite jeans after Thanksgiving.

They then announced to the world that AGW was true --
because their models said it was.

But a model fitting old data is not direct evidence that
the theory
behind the model is true. Many alternate models can fit that data
equally well. It is a necessary requirement for any model, were it
true, to fit the data, but because it happens to is not a proof that
the model is valid.

For a model to be believable it must
make skillful
predictions of independent data. It must, that is, make accurate
forecasts of the future. The AGW models have not yet done so. There is,
therefore, no direct evidence for AGW.

The models predicted warmer temperatures, but it got
cooler. One of
the revealed CRU emails found one prominent gentlemen saying, "We can't
account for the lack of warming at the moment and it is a travesty that
we can't."

It is. But only if you were concerned that the AGW
theory will be nevermore.

William
M. Briggs is a statistical consultant in New
York and San
Francisco. He is an American Meteorological Society member and serves
on their Probability & Statistics Committee. His specialty is
on
the philosophy of evidence, forecast evaluation, and marketing.